Just to compliment the DNA Obfu of Ranna, here's my own first obfu, dnareader.pl:

#!/usr/bin/perl
# Run as dnareader.pl TCCCTCATTGAATCCAAACC
# You'll get a ++ from me if you can make it say "perl"
# instead.
$"='ATCG';
foreach (split '', shift) {
$;++;$,=$,<<2|index $",$_;
next if
$;&3;$,=print chr $,;$,--;
}

Warning: Unless otherwise stated, code is untested. Do not use without understanding. Code is posted in the hopes it is useful, but without warranty. All copyrights are relinquished into the public domain unless otherwise stated. I am not an angel. I am capable of error, and err on a fairly regular basis. If I made a mistake, please let me know (such as by replying to this node).